Field of the Invention
The present invention relates to a brightness level compensation of a video display apparatus, and more particularly, to a circuit for controlling a contrast level and compensating a brightness level of a video display apparatus capable of simplifying a circuit configuration and reducing a cost of production by placing a brightness level compensation circuit in a video pre-amplifier for improving a brightness deflection of an image displayed in the peripheral regions of a display screen of the video display apparatus.
Description of the Prior Art
In general, images displayed on a video display apparatus, such as a monitor of a computer system, have a different brightness according to the display positions of the images on the screen.
That is, fluorescent materials arranged on a center portion of a fluorescent screen of the video display apparatus such as a cathode-ray tube has a smaller size than fluorescent materials arranged on upper, lower, left and right portions of the fluorescent screen of the video display apparatus. Also, a glass thickness of the upper, lower, left and right portions of the fluorescent screen is thicker than the glass thickness of the center portion thereof.
Accordingly, the brightness of respective portions of the image displayed through the fluorescent screen is not uniform. Therefore, when the brightness of the image controlled by a brightness control signal at the center portion is also controlled by the same brightness control signal at the peripheral display portions of the screen, the image displayed at the peripheral portions is darker than the image at the center portion. That is, a brightness deflection occurs.
To improve the brightness deflection as described above, an apparatus having a compensation circuit which supplies a control signal for compensating the brightness deflection had been contemplated. However, since such a compensation circuit for the brightness deflection compensation is arranged on a printed circuit board separate from a video pre-amplifier, the circuit configuration becomes complicated and the cost of production largely increases.
Therefore, it is an object of the present invention to provide a circuit for compensating a brightness level of a video display apparatus capable of simplifying a circuit configuration and reducing a cost of production by placing a brightness level compensation circuiting a video pre-amplifier of the video display apparatus for improving a brightness deflection of an image displayed on a peripheral portion of a screen.
It is another object of the present invention to provide a circuit for controlling a contrast level and compensating a brightness level of a video signal displayed in a video display apparatus having a simplified circuit configuration and reduced cost of production by placing contrast controller and a brightness level compensation circuit in a video pre-amplifier of the video display apparatus for improving the contrast level and a brightness deflection of an image displayed on a peripheral portion of a screen.
In order to achieve the above objects, the present invention provides a circuit for compensating a brightness level of a video display apparatus having a microprocessor for memorizing a predetermined data for a brightness level compensation and outputting a data signal and a clock signal based on the predetermined data for the brightness level compensation, and a video pre-amplifier for receiving a video signal and horizontal and vertical fly-back pulse signals and compensating a contrast level and a brightness level of the video signal in accordance with the data signal and the clock signal to output a compensated video signal.
In order to achieve the above objects, the present invention provides a circuit for compensating a brightness level of a video display apparatus having a microprocessor for memorizing a predetermined data for a brightness level compensation and outputting a data signal and a clock signal based on the data for the brightness level compensation, a video pre-amplifier having a digital controller for outputting a first control signal to control the contrast level of the video signal and a second control signal to compensate the brightness level of the video signal in response to the data signal and the clock signal, a brightness level controller for receiving the horizontal and vertical fly-back pulse signals and outputting a brightness level compensation signal to compensate the brightness level of the video signal in response to the second control signal, and a contrast controller for controlling the contrast level in response to the first control signal and compensating the brightness level of the video signal in response to the brightness level compensation signal to output the compensated video signal.
According to the circuit for compensating the brightness level of the video display apparatus of the present invention, the brightness level compensation circuit for compensating the brightness deflection of each portion of the screen is arranged in the video pre-amplifier of the printed circuit board.
Accordingly, the design of the brightness level compensation circuit is simplified and the size of the printed circuit board is reduced. In addition, the cost of production decreases and the is productivity of products increases by reducing a number of components of the brightness level compensation circuit.